1. Field of the Invention
The present invention is related to an apparatus for stabilizing the spine when spinal discs have deteriorated. More particularly, the present invention is related to an apparatus for replacing damaged spinal discs and vertebral bodies.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. Sections 1.9-1.99.
The spine, particularly the human spine, is composed of many vertebral bones stacked one upon the other, with an intervertebral disc between each pair of adjacent vertebral bones. The discs act as cartilaginous cushions and shock absorbers. The spinal cord runs in a bony canal formed by successive openings in these bones. The spinal nerves exit the spinal cord from small openings in the vertebral bodies and supply nerves and nerve signals to and from other body structures.
Damage to the structure of this system may arise from several causes. Accidental fractures of the bones leads to disruption and collapse of spinal discs and hence pinching of important nerves in the spinal cord. Collapsed, herniated or bulging discs can also pinch the nerves in the spinal cord or nerves exiting the spinal cord. Post operative scarring often lead to disruption of the spinal cord and associated structures.
Surgery is often required to reconstruct the vertebral bodies, remove the herniated discs, and to implant certain hardware to stabilize the spine. Such hardware typically comprises rods, screws, and plates. A scaffolding is formed to lift and hold the bony structures formed by the vertebral bones. Unfortunately, many of these hardware structures fail when they lose bony purchase, pierce unwanted structures, and so forth. Further, many of these structures unnecessarily limit the patient's range of spinal motion, particularly rotational movement. Many such structures, for example, the spine discs disclosed in U.S. Pat. Nos. 5,676,702, 5,645,599 and 5,702,450, tend to deteriorate over time and so cannot be considered permanent.
Therefore, a need exists for a vertebral body prosthesis that does not lose bony purchase over time, that does not unnecessarily limit the patient's range of spinal motion, particularly rotational movement, and that is stable over a long period of time.